1. Field of the Invention
The present invention relates to a non-contact electrostatic recording apparatus which forms an electrostatic recording image without bringing its recording head into contact with a recording medium.
2. Description of the Related Art
Conventionally, a multi-stylus printer is known well as one type of an electrostatic recording apparatus. In a multi-stylus printer, a large number of needle-like recording electrodes are arranged in the main scanning direction at a very small equal pitch to constitute a recording head. A voltage is selectively applied to the needle-like electrodes in accordance with a recording signal. Electrical discharge is performed directly onto a recording sheet to form an electrostatic latent image. In this case, a special paper sheet coated with an agent having a high electric resistance is used so that charges can be easily and stably held on the sheet. However, such a special sheet is not suitable to be written with a pencil or a pen. In addition, it can be deteriorated by environmental conditions such as humidity and thus cannot be kept stored for a long period of time. Therefore, this type of paper is not suitable for office use.
When a gap between the distal ends of the needle-like electrodes and the sheet surface is large, the electric field is spread to increase the size of the dot to be formed, making it difficult to obtain a recording image having a high resolution. For this reason, a gap material is provided for the sheet surface. The gap material and the distal ends of the needle-like electrodes are brought into slidable contact with each other so that a very small gap can be maintained. In this case, however, the distal ends of the needle-like electrodes are worn.
In order to use ordinary paper and to correctly keep the very small gap between the image medium and the distal ends of the recording electrodes, a method is adopted to preliminarily form a toner image on a drum-like intermediate recording medium and to transfer the toner image on a sheet. With this method, since the intermediate recording medium is used, the entire system tends to become large in size. In order to avoid this size increase, a process for performing both recording and developing simultaneously is often employed. In this case, the recording electrodes are arranged along the widthwise direction (main scanning direction) of the developing agent convey path. The developing agent is supplied in the sub-scanning direction perpendicular to the main scanning direction and is selectively transferred onto the intermediate recording medium from the recording electrodes, thereby forming a toner image.
However, the recording electrodes are present in the developing agent supply direction. In order to prevent the recording electrodes from interfering with the developing agent supply, a large number of holes for allowing the developing agent to pass therethrough must be formed at portions of a film substrate or the like constituting the recording electrodes excluding the portions of the recording electrodes, and the developing agent must be supplied through these holes. When these holes are formed, however, they pose restriction on the space to arrange the recording electrodes on the film substrate. As a result, high-density recording electrodes cannot be arranged, and a recording apparatus with a high printing resolution cannot be obtained.